Originally posted by Rogerm60:
(551) The 95 has no way to know wether the IMRC is open or closed.





Correct, however... It can tell if the PCM's driver circuit is behaving correctly as it would if the IMRC were working properly. There is no feedback sensing beyond that since there is no sensor directly on that solenoid.

The PCM has an internal sensing capability on the line that controls the IMRC solenoid. The output pin of the PCM would normally be at Vbatt when the solenoid is not energized. To energize it, the PCM "grounds" that pin, allowing current flow through the solenoid and actuating it.

If the internal monitor circuit does not see this transition from Vbatt to ground when it is expected, it will cause the PCM to report the 551 error.

Possible causes: Loss of Vbatt to IMRC solenoid, open solenoid, open connection between the solenoid and the PCM output pin, internal PCM failure (driver circuit), or internal PCM failure (sensing circuit).

Check and make sure the IMRC solenoid is not unpluuged is the simples check.

Steve

98 Contour SE Sport 2.5 Duratec ATX The wifey's car 89 Taurus SHO - 246K miles 94 SHO ATX - 190K 1997 F-150 5.4L ATX - The Workhorse 150K. ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!